Description:

What issue is being seen? Describe what should be happening instead of
the bug, for example: Envoy should not crash, the expected value isn't
returned, etc.

If an error is returned during extproc's request/response header/body processing, the error is not returned to the user. This causes user to keep waiting for a response until it eventually timesout

expected
an error message should be immediately returned to the user.

Repro steps:

Include sample requests, environment, etc. All data and inputs
required to reproduce the bug.

Explicitly return a fake error in any of the extproc's processing methods (eg. requestBodyProcessing) and send a request to it.

Note: If there are privacy concerns, sanitize the data prior to
sharing.

Environment:

Include the environment like gateway version, envoy version and so on.

Logs:

Include the access logs and the Envoy logs.

Example logs.

time=2025-07-08T11:16:40.329-04:00 level=ERROR msg="error processing request message" error="cannot process request headers: failed to transform request: fake Error"

Possible Cause
Error returned from processMsg() here is never streamed back to user

Instead ProcessingResponse_ImmediateResponse should be returned to the user